1. Field of the Invention
The present invention relates to a sensor system used for controlling a motor, and more particularly, to a novel improvement for providing a fail-safe sensor system used for controlling a motor, which is small in size and low in price, and has high reliability and dynamic characteristics without using newly providing other system sensors.
2. Description of the Related Art
As a device of this type which has been employed up to now, there is a structure of a resolver as a sensor for controlling a motor, shown in FIG. 2A.
In FIG. 2A, reference numeral 1 denotes a resolver that detects the rotation angle of a brushless motor 2, and an angle signal 1a of the resolver 1 is converted into a digital signal by an R/D converter 3 and then inputted to a servo controller 4 that conducts drive control of the brushless motor 2. The brushless motor 2 is driven under control by using the rotation angle which is detected by the resolver 1.
Also, FIG. 2B is a diagram showing the structure of a device that estimates the rotation angle by using a counter electromotive voltage of the motor.
In the structure shown in FIG. 2B, the rotation angle of the brushless motor 2 is estimated on the basis of the counter electromotive voltage which is detected from the brushless motor 2, and an estimate value of the rotation angle is inputted to the servo controller 4, to thereby drive the brushless motor 2 under control.
However, the resolver shown in FIG. 2A is exclusively used as a sensor for rotation control of the brushless motor 2, but does not pay attention to the dynamic characteristics and does not positively aspire the effective utilization of the bruthless motor 2.
Also, although the estimate of the rotation angle of the brushless motor 2 in the structure shown in FIG. 2B is suitable for an intended use as the redundant system for fail-safe, there arises such a problem that smooth control is extremely difficult because stable rotation is not obtained due to load fluctuation or the like and the rotation vibration becomes large, and there also arises such a problem that stop or low-speed control is difficult. Thus, there arise many problems upon using the conventional device as a main detecting system.
The present invention has been made to solve the above-mentioned problems with the conventional art, and therefore an object of the present invention is to maintain and improve the global environment suffering a reduction of a coal oil resource by the diffusion of an electric motive energy for a good cause, and more particularly to provide a sensor system used for controlling a motor, which is small in size, and low in price, and has high reliability and dynamic characteristics without using new other system sensors.
According to the present invention, there is provided a sensor system for controlling a motor in a motor drive control system having a drive control circuit that controls the driving of a motor in accordance with an operation command, the system comprising a main angle detecting means having a resolver that detects the rotation angle of the motor; and a sub angle detecting means that estimates the rotation angle of the motor on the basis of the counter electromotive power of the motor. In this system, the main angle detecting means detects the rotation angle of the motor in a normal state, and the sub angle detecting means detects the rotation angle of the motor when the main angle detecting means is in failure. Further, the sub angle detecting means includes a counter electromotive voltage detecting means that detects the counter electromotive voltage of the motor, and an angle estimating means that estimates the rotation angle of the motor on the basis of the counter electromotive voltage.